P1

P1

1. The solar system

   • Centre= Sun
   • Eight planets= MVEMJSUN
   • Asteroids= irregular lumps or rock
   • Comets= small objects of rock and ice (have elongated orbits around the sun.
   • Dwarf planets= spherical lumps of rock

2. The universe

   • We can only see stars as they were in the past
     • One light year= 9.5 million million km
     • Light travels through a vacuum at 300000 km/s

3. Distance to stars

   • Brightness
     • Same real brightness doesn't = same relative brightness
       • Further away= smaller relative brightness
       • Negatives
         • Need to know the distance of one the stars
           • Only works if have same real brightness
           • Dust, rain, clouds, light pollution
   • Parallax
     • As earth orbits close stars move slightly against fixed background
       • However, can only be used of nearby stars

4. Expanding universe

   • Redshift
     • Redshift is the light coming from distant galaxies
       • As galaxies move away, the wavelength increases
         • Most galaxies appear to be moving away from us
           • further away from earth a galaxy is, thefaster it is moving away from us

5. Fusion of elements in stars

   • Nuclear fusion= only at high densities and temp
     • hydrogen nuclei hit each other so hard= helium= lots of energy= nuclear fusion
       • This is how all chemical elements with atoms heavier than helium were made
         • These elements spread through space when stars explode
           • Stars end their lives as a supernova
             • Massive explosion
               • Where all the different chemical elements are made

6. The changing earth

   • breaks in earths crust= new volcanoes& mountains
     • Sediments crushed together= sedimentary rock (formed in seas)
       • Collisions between different parts of the crust= mountains
         • Rocks provide evidence for this

7. P1

   • The big bang
     • detection of cosmic background radiation= evidence
       • Sun= 5000 million years ago
     • Earth= 4500 million years ago
       • Universe expanded rapidly from single point 14000 million years ago
   • Continental drift
     • Alfred Wegener 1915
       • Millions of year ago= one land mass
         • Then it split into continents which drifted apart
           • Continents move because they sit on mantle
             • The rocks move slowly by convection currents
               • Based on the way the all fit
                 • And that similar fossils and rocks were found of continents now separated by oceans
     • Oceanic ridges
       • Form when sea spreads and liquid rock fills gap
         • This rock is magnetised by earths field
           • Each time earths field reverses, it is shown in the rock
             • The seafloor increases by cm's/year= seafloor spreading
   • Tectonic plates
     • Volcanic mountains= one tectonic plate forced under another
       • Earths crust has solid tectonic plates
         • Meet at plate boundaries
           • Fold mountains= when 2 tectonic plates meet head on
       • Earthquakes form= when they slide past each other
   • Seismic waves
     • S-waves= move slowly through solid
       • Can use these to work out the structure of the earth
         • Formed when two plates move suddenly
           • P-waves= move quickly through solids and liquids
             • seismometers record them
   • Structure of the earth
     • Mantle= solid rock
       • Outer core= liquid nickel and iron
         • Inner core= solid nickel and iron
           • Mantle= semi-liquid rock
   • Waves
     • Transfers energy away from a vibrating sorce
     • Wavelength= distance between each peak
     • Wave speed= FxWL
       • Higher the frequency the shorter the wave length
         • Frequency= Number of vibrations in one second
           • Amplitude= maximum height of the wave
           • Unit of frequency is hertz (Hz)